Research article

Subtelomeric study of 132 patients with mental retardation reveals 9 chromosomal anomalies and contributes to the delineation of submicroscopic deletions of 1pter, 2qter, 4pter, 5qter and 9qter

Marie Sogaard¹ , Zeynep Tümer² , Helle Hjalgrim^1,3 , Johanne Hahnemann¹ , Birgitte Friis⁴ , Paal Ledaal⁵ , Vibeke Faurholt Pedersen³ , Peter Baekgaard³ , Niels Tommerup² , Sultan Cingöz^2,6 , Morten Duno⁷ and Karen Brondum-Nielsen¹

¹The John F. Kennedy Institute, Glostrup, Denmark

²Wilhelm Johannsen Centre for Functional Genome Research, IMBG, The Panum Institute, University of Copenhagen, Denmark

³Department of Paediatrics, Glostrup Hospital, Denmark

⁴Department of Paediatrics, Roskilde Hospital, Denmark

⁵Department of Paediatrics, Sonderborg Hospital, Denmark

⁶Department of Medical Biology and Genetics, Dokuz Eylul University, Faculty of Medicine, Izmir, Turkey

⁷Department of Clinical Genetics, Rigshospitalet, Denmark

author email corresponding author email

BMC Medical Genetics 2005, 6:21doi:10.1186/1471-2350-6-21

Published:	17 May 2005

Abstract

Background

Cryptic chromosome imbalances are increasingly acknowledged as a cause for mental retardation and learning disability. New phenotypes associated with specific rearrangements are also being recognized. Techniques for screening for subtelomeric rearrangements are commercially available, allowing the implementation in a diagnostic service laboratory. We report the diagnostic yield in a series of 132 subjects with mental retardation, and the associated clinical phenotypes.

Methods

We applied commercially available subtelomeric fluorescence in situ hybridization (FISH). All patients referred for subtelomeric screening in a 5-year period were reviewed and abnormal cases were further characterized clinically and if possible molecularly.

Results

We identified nine chromosomal rearrangements (two of which were in sisters) corresponding to a diagnostic yield of approx. 7%. All had dysmorphic features. Five had imbalances leading to recognizable phenotypes.

Conclusion

Subtelomeric screening is a useful adjunct to conventional cytogenetic analyses, and should be considered in mentally retarded subjects with dysmorphic features and unknown cause.